A fan equipped with variable pitch blades makes it possible to adjust the pitch (and more specifically the pitch angle) of the blades depending on flight parameters, and thus to optimize the operation of the fan, and of the propulsion unit in general in which such a fan is incorporated. As a reminder, the pitch angle of a blade corresponds to the angle, in a longitudinal plane perpendicular to the axis of rotation of the blade, between the chord of the blade and the plane of rotation of the fan.
In order to be certified, such a fan must include a feathering device for feathering the blades, in other words a device for positioning the blades in a position in which said blades are nullified as much as possible with respect to the direction of advance. In general, in the feathered position, the pitch angle of the blades is 90°. The blades are, for example, set in the feathered position during a failure (for breakdown) of the pitch control device of the blades (for example a failure of a hydraulic actuator) in order that said blades offer the least possible resistance (drag).
In order to increase the performance of the fan, engine manufacturers are continually seeking to reduce the hub ratio of the fan. This hub ratio is the quotient of the diameter of the outer envelope of the feet of the blades at the leading edge of the blades, divided by the diameter of the circle passing through the outer radial ends of these blades. For an equal fan diameter, the reduction in the hub ratio, i.e. in the diameter of the outer envelope, implies an increase in the suction cross-section of the fan, in other words an increase in the treated flow, and consequently an increase in its propulsive performance.
Conventionally, the feathering device of the blades is located, in an enclosure, radially located between the control device for the pitch of the blades and the blade pivots, the blade pivots being specific to each blade or common to all blades.
The fan comprises a rotor that can move with respect to a fixed housing, the rotor carrying a series of variable-pitch blades. The rotation of the rotor is guided with respect to the fixed housing by means of a plurality of bearings. Given the operating conditions, namely heavily loaded bearings subject to high velocities, the bearings require lubrication by means of a liquid lubricant (generally oil).
However, the lubricant must not adversely affect the operation of the internal devices (and in particular of the device for feathering the blades) present in the enclosure, for example by contaminating these devices through a deposit of impurities. On the other hand, the lubricant must not remain trapped (or stored) in the cavities of the enclosure so as not to create imbalances harmful to the dynamic equilibrium of the rotor of the fan.
Examples of related systems and devices can be found in documents US 2014/205457 A1, FR 2977636 A1, WO 2014/013201 A1, FR2918120 A1, and U.S. Pat. No. 5,272,868, the complete disclosures of which are incorporated herein by reference.
In one aspect, the present disclosure provides a fan module which responds to the above-mentioned constraints.